JPH03218442A - Differential refractometer - Google Patents

Abstract

PURPOSE:To cancel the deviation in the formed image position due to vibration, etc., and to improve precision in measuring the refractive index by providing the light transmitting member and image sensor conjugately arranged with respect to a source light condensing lens and simultaneously detecting the beams transmitted through two identification sites of the image carried by the light transmitting member. CONSTITUTION:The light from its source 21 is split by a slit 24 into beams L1 and L2, and the beams are transmitted through a cell 27, reflected by a reflecting mirror 28 and again transmitted through the cell 27 to form the image of the slit 24 on a unitary image sensor 29. The slit 24 and the sensor 29 and conjugately arranged with respect to an image forming lens 25. The first chamber 71 of the cell 27 is filled with a sample soln., and the second chamber 72 with a reference such as a solvent. The reflected beam L1 is transmitted through only the solvent, the beam L2 is transmitted through the sample soln. and solvent, the hence both beams are surely split to form an image on the detecting face of the sensor 29.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a differential refractometer used, for example, for determining molecular weight.

BACKGROUND ART Techniques have been known for measuring the molecular weight of a sample, which is a solute, by measuring the refractive index of a solution and its concentration dependence. To measure the refractive index of a sample solution in this way, for example, a cell consisting of a transparent container separately containing the sample solution and its solvent is used, and when monochromatic light is incident on this cell through a slit, the sample solution and the solvent are This can be done by taking advantage of the fact that the optical path of incident light is bent depending on the difference in refractive index between the two. In this way, it takes advantage of the fact that incident light is deflected according to the refractive index difference between a reference with a known refractive index (in the example above, the solvent of the sample solution) and a sample (sample solution) with an unknown refractive index. A differential refractometer is used to measure the refractive index of a sample.

The basic configuration of a conventionally used differential refractometer is shown in FIG. Light from a light source 1 is guided to a collimator lens 3 through a slit 2 and is made into parallel light. This parallel light becomes a light beam A whose width is limited by the slit 4 and enters the cell 5. Luminous flux A from this cell 5
An image of the slit 4 is formed from the imaging lens 6 through a correction glass plate 7, which will be described later, on the detection surface of a photosensor 8 disposed on the focal plane of the imaging lens 6. Correction glass 7
is angularly displaced in the direction of arrow R1 by operating the dial 9.

FIG. 22 is a cross-sectional view showing the structure of the cell 5 in an enlarged manner. This cell 5 is called a price cell, etc., and the internal space of a cell container 5a composed of a square columnar transparent cylinder is diagonally partitioned by a partition plate 5b to form a first chamber 5l and a second chamber 52. This is what I did.

For example, when the first chamber 5l is filled with a sample solution whose refractive index is to be measured and the second chamber 52 is filled with the solvent,
The light beam A from the slit 4 is deflected in accordance with the difference in refractive index between the sample solution and the solvent.

When measuring the refractive index, the first step is
Filling both the chamber 5l and the second chamber 52 with the same solvent,
The image of the slit 4 is detected by the photosensor 8. Then, as a second procedure, for example, a sample solution is placed in the first chamber 5l, a solvent is placed in the second chamber 52, and the same measurement is performed. The imaging position of the slit image changes between the first and second steps in accordance with the amount of deflection that the light beam A receives.

The refractive index difference Δn is Δn=ms−nw taroθ...
■However, n8...Refractive index of the sample solution n6...Refractive index of the solvent e...Refractive index outside the cell α...Deflection angle θ of the light flux 8...The difference between the light flux A and the partition plate 5b It is expressed like an angle. In equation (2), one of the codes is selected depending on the values of the refractive index nl+nl and the angle θ. On the other hand, if the distance between the cell 5 and the photosensor 8 is l, then using the displacement ΔX of the imaging position of the slit image, s
inα is ΔX S1 ro α=
... ■l Since it is expressed as, the above formula (■) can be transformed as follows. In the air, it is e#1, so the result is as follows. That is, if the displacement ΔX is known, the refractive index difference Δn can be obtained, and therefore the refractive index of the sample solution can be determined based on the refractive index of the solvent.

FIG. 23 is a plan view for explaining the function of the correction glass plate 7. By operating the dial 9, the correction glass plate 7 is moved to its reference position 7a (the position indicated by the broken line in FIG. 23).
When the angle β is angularly displaced from the angle β, the angle of incidence of the light beam 8 on the correction glass plate 7 becomes equal to the angle β. At this time, if the optical path is shifted by ΔX' due to the refraction of the luminous flux A, then the displacement ΔX' of this optical path is approximately expressed as ΔX'o
Csinβ...■.

Therefore, first, with the correction glass plate 7 in the reference position 7a, both chambers 51 and 52 of the cell 5 are filled with a solvent, and the light flux A is detected by the photo sensor 8, and then the first chamber 51 of the cell 5 is filled with a solvent. When the deflected light beam A when filled with the sample solution is imaged on the photosensor 8 by operating the dial 9, the displacement ΔX' of the optical path of the light beam 8 due to the correction glass plate 7 is Δx ′■ΔX... ■.

The displacement ΔX' is determined from the value of the dial 9, and therefore, based on the value of the dial 9, the refractive index difference Δn between the sample solution and its solvent can be determined from the above equation (2).

In such a configuration, there is a risk that individual differences among operators may appear when shifting the imaging position of the slit image by manual operation of the dial 9, resulting in poor data reproducibility and, as a result, refractive index measurement. This resulted in a deterioration in accuracy.

Other prior art that solved this problem is, for example, Japanese Patent Application Laid-open No. 63
It is disclosed in Japanese Patent No. 188744, and its basic configuration is shown in FIG. The light from the light source 11 is
The light is condensed by a condenser lens l2, further narrowed down by a slit l3, and made into a thousand lines of light by a collimator lens l4. This 1,000-line light is a V block 15 made of a transparent material with a known refractive index.
incident on . This V block 15 has a V-shaped recess 15a with an apex angle of 90 degrees, and uses this recess 15a as a sample stage. In this recess 15a, a sample 16 with an unknown refractive index whose apex angle is, for example, 90 degrees is placed, and approximately half of the parallel light from the collimator lens l4 is transmitted through this sample l6.

■The light from the block 15 passes through a chopper l7 and is focused by an imaging lens 18, and enters a one-dimensional image sensor l9 composed of a one-dimensional CCD (charge-coupled device) or the like to form an image of the slit l3. . The chopper l7 includes: (1) a fixed piece 17a formed with an aperture corresponding to the light transmitted through the sample l6 among the light from the block l5 and an aperture corresponding to the light not transmitted through the sample l6; and one of the apertures. and a movable piece 17b that blocks the.

In measuring the refractive index of the sample 16, first, the light transmitted through the sample 16 is blocked by the chopper 17.

The imaging position of the slit image at this time is detected by the one-dimensional image sensor 19, and is held by, for example, a control means (not shown). In this case, the light passing through the optical fiber 17 is not deflected because it is the light that has passed only through the V-bronch 15, which has a uniform refractive index.

Next, the chopper 17 cuts off the light from the V block 15 that does not pass through the sample 16. As a result, light that has been deflected in accordance with the refractive index difference between the block 15 and the sample 16 enters the imaging lens 18. Therefore, the slit image will be formed at a different position than in the above case, corresponding to the refractive index difference. This imaging position is detected by the one-dimensional image sensor l9 and taken into the aforementioned control means. This control means calculates the distance between the imaging positions of the slit images formed by the light passing through the sample 16 and the light not passing through the sample 16, respectively.

From this calculation result, the difference in refractive index between the sample 16 and the V block 15 is determined, as in the case of the first prior art shown in FIG. 21 described above.

In the prior art shown in FIG. 24, the amount of deflection is measured based on the output of the one-dimensional image sensor l9 without requiring manual operation, and therefore the refractive index is easily measured. Furthermore, since measurement errors due to individual differences among measurement operators do not occur, measurement accuracy is improved.

Problems to be Solved by the Invention A new problem with the above-mentioned prior art is that vibrations occur when the movable piece 17b of the chopper 17 is driven, and this vibration causes the formation of a slit image on the one-dimensional image sensor 19. The image position is displaced, resulting in a deterioration in measurement accuracy, and the presence of mechanically driven parts increases the number of parts.

Furthermore, in the first prior art shown in FIG. 21, in addition to the problem of poor data reproducibility due to individual differences in measurement operators as described above, when the compartment of cell 5 is filled with solvent, Since the detection of the slit image in the cell 5 and the detection of the slit image when the first chamber 5l of the cell 5 is filled with the sample solution are performed with a certain time interval, it is possible to detect the slit image at a certain time interval. There is also a problem in that error factors such as changes over time and the effects of deflection due to changes in the optical base (not shown) over time are introduced, which further deteriorates measurement accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a differential refractometer that solves the above-mentioned technical problems and has significantly improved measurement accuracy.

Means for Solving the Problems> A differential refractometer according to claim 1 for achieving the above object includes: a light source; a light transmitting member carrying an image having at least two identification points; a lens for condensing light source light transmitted through the member; an image sensor disposed at a position conjugate with the light transmitting member with respect to the lens; and an image sensor located at any position between the light transmitting member and the image sensor. a cell that separately accommodates a sample whose refractive index is to be measured and a reference having a reference refractive index; The device further includes a diaphragm member that narrows down the light that has passed through the two identification points of the transmission member, and allows at least one of the narrowed lights to pass through the cell.

In the differential refractometer according to claim 2, the light that has passed through one of the two identification points is transmitted through both the sample and the reference in the cell, and the light that has passed through the other identification point has passed through the cell. It was designed to pass outside.

In the differential refractometer according to a third aspect of the present invention, the light passing outside the cell is propagated through the air.

In the differential refractometer according to a fourth aspect of the present invention, an empty cell containing air is interposed in the optical path of the light passing outside the sensor.

The differential refractometer according to a fifth aspect of the present invention is characterized in that a solid cell made of a transparent solid material is interposed in the optical path of the light passing outside the cell.

In the differential refractometer according to claim 6, the diaphragm member converts the light that has passed through the two identification points onto the cell and the light that passes through one of the sample and the reference. The light is focused on light that passes through both the reference and is deflected according to the difference in refractive index between the two.

<Function> According to such a configuration, for example, one of the at least two identification points supported on the light transmitting member! The light that has passed through one spot passes through the cell and forms an image on one spot on the detection surface of the image sensor, and the light that has passed through another identification spot passes through the cell or outside the cell and forms an image on another spot on the detection surface of the image sensor. The image is focused on the spot. These lights are simultaneously detected by the image sensor, and from the output of the image sensor, it is possible to determine the distance between the imaging positions of the light that has passed through each of the identification points. The distance between the imaging positions corresponds to the amount of deflection that the light that has passed through the cell receives in response to the mutual refractive index difference between the sample and the reference. Therefore, the refractive index difference between the sample and the reference can be determined based on the output of the image sensor.

The arrangement of the present invention does not include mechanically driven components, thus overcoming the problem of deterioration of measurement accuracy due to vibrations. In addition, since the light that has passed through the two identification points of the light-transmitting member is detected simultaneously by the image sensor, even if the imaging position of one light is shifted due to vibration or air fluctuation, the other light will be The image position also exhibits a similar change, and therefore, by determining the distance between each image formation position of the light that has passed through the identification point, it is possible to offset the deviation of the image formation position due to the vibration.

Note that since the light transmitting member and the image sensor are arranged in a conjugate positional relationship with respect to the lens, it is possible to clearly form an image of the light transmitting member on the detection surface of the image sensor. In addition, the diaphragm member reliably separates the light that has passed through the two identification points of the image carried by the light-transmitting member, so that one of the lights passes through one optical path within the cell, for example, an optical path that passes only through either the sample or the reference (
The other light path passes through the other light path inside the cell, for example, the light path that passes diagonally through the interface between the sample and the reference. can be reliably separated on the detection surface. In this way, the accuracy of measuring the distance between the imaging positions of the light that has passed through the identified location is improved.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments.

FIG. 1 is a plan view showing a simplified basic configuration of a differential refractometer according to an embodiment of the present invention, and FIG. 2 is a front view thereof. The light from the light source 2l passes through the interference filter 22 and is focused by the condensing lens 23, and as shown in FIG.
A slit 24 having elongated openings 24a and 24b at certain locations.
The luminous flux Ll. Generate L2. In this embodiment, the slit 24 constitutes a light transmitting member.

Luminous flux L1 from the slit 24. L2 enters the cell 27 from the imaging lens 25 via an aperture 26, which is a diaphragm member having a via hole or the like formed on the optical axis of the imaging lens 25, for example. The luminous flux L1. transmitted through the cell 27. After being reflected by the reflecting mirror 28, L2 passes through the cell 27 again and forms an image of the slit 24 on the one-dimensional image sensor 29.

The slit 24 and the one-dimensional image sensor 29 are arranged in an optically conjugate positional relationship with respect to the imaging lens 25, so that the aperture 24a of the slit 24 is located on the detection surface of the one-dimensional image sensor 29. 24b is clearly formed. A light-shielding cut plate 30 prevents excess surrounding light from entering the one-dimensional image sensor 29.

FIG. 4 is a cross-sectional view of the cell 27. This senore 27 has a first chamber 7 formed by diagonally partitioning the interior space of a senore container 27a formed of a square prism-shaped transparent cylinder with a transparent partition plate 27b.
For example, the first chamber 7l is filled with a sample such as a sample solution whose refractive index is to be measured, and the second chamber 72 is filled with a reference such as its solvent.

The luminous flux L2 passes through the partition plate 27b from the second chamber 72 and enters the first
The luminous flux Ll passes through the chamber 7l to the reflecting mirror 28, and the luminous flux Ll enters the second chamber 7.
Only 2 is transmitted. Luminous flux L after being reflected by the reflecting mirror 28
l. L2 advances in a direction substantially opposite to that shown in FIG. In this way, the light beam L2 passes through both the sample solution in the first chamber 7l and the solvent in the second chamber 72, and the light beam L2 passes through both the sample solution in the first chamber 7l and the solvent in the second chamber 72.
Since l passes only through the solvent, the light beam L2 is deflected in accordance with the refractive index difference between the sample solution and its solvent, and the light beam Ll is not deflected due to the refractive index difference. Therefore, the distance between the imaging positions of the images of the apertures 24a and 24b of the slit 24 detected by the one-dimensional image sensor 29 corresponds to the refractive index difference between the sample solution and the solvent. The same applies when the first chamber 7l is filled with a solvent and the second chamber 72 is filled with a sample solution, and the light beam L2 transmitted through the partition plate 27b is deflected according to the refractive index difference, and only the second chamber 72 is filled with a sample solution. The light beam Ll that passes through is not deflected due to the difference in refractive index.

An aperture 26 provided behind the imaging lens 25 allows the light beam L1. L2 is narrowed down sufficiently to ensure that the luminous flux L2 reaches cell 2.
The light beam Ll is transmitted through the partition plate 27b of the cell 27, and the light beam Ll is transmitted only through the second chamber 72 of the cell 27. As a result, on the detection surface of the one-dimensional image sensor 29, there is a light beam L2 that has passed through both the sample solution and its solvent, and a light beam L2 that has passed only through the solvent. and are reliably separated and imaged.

FIG. 5 is a perspective view for explaining the measurement principle, and shows how the light beams Ll and L2 form images on the detection surface of the one-dimensional image sensor 29. Is there a sample in both the first chamber 7l and the second chamber 72 of the cell 27? When the liquid solvent is filled, the light beam L2 is not deflected and follows the optical path L. , to the detection surface of the one-dimensional image sensor 29. The imaging position S IEF of the light beam L2 when it is not subjected to this deflection, and the first
Polarized light beam L2 when sample solution is placed in chamber 7l
The positional deviation ΔX from the imaging position S2 corresponds to the difference in refractive index between the sample solution and its solvent. One-dimensional image sensor 2
What is detected at 9 is the imaging position Sl of the light beam Ll and the light beam L
The distance ΔXI between the image forming position S1.2 and the image forming position S2 is ΔXI. If the distance ΔXO between S and S is determined in advance, the positional deviation ΔX (=ΔXI - ΔXO) can be determined.

In this embodiment, the optical path is turned back by the reflecting mirror 28, and the light beam L1. Since the light beam L2 is caused to pass through the cell 27 twice, the light beam L2 is deflected twice. Therefore, the positional deviation ΔX is, for example, the second
This corresponds to twice the amount of displacement of the slit image in the case of the conventional configuration shown in FIGS. 1 and 24. Therefore, in the differential refractometer of this example, the refractive index difference Δn is
It is obtained by replacing ΔX in the formula with ΔX/2, and the result is A'' tan θ. However, the angle θ is the difference between the luminous flux L2 and the partition plate 2 of the cell 27.
7b (see FIG. 4), and l is the distance from the cell 27 to the detection surface of the one-dimensional image sensor 29.

Furthermore, the spacing between elements (not shown) such as photodiodes in the one-dimensional image sensor 29 is 5.
6 X 1 0-" (am), then ΔX=m ・5 due to the number of elements m between the imaging positions of the slit image
6 x 1 0-" (mm)
) 2●l jtanθ ... ■ It is transformed.

FIG. 6 is a diagram showing the output signal intensity of the one-dimensional image sensor 29, in which the horizontal axis represents the one-dimensional coordinates taken on the detection surface of the one-dimensional image sensor 29, and the vertical axis represents the output signal intensity. The peak PI corresponds to the luminous flux Ll, and the peak P2a
corresponds to the luminous flux L2 when the first chamber 7l is filled with a solvent, and the peak P2b corresponds to the luminous flux L2 when the first chamber 71 is filled with a sample solution. The distance ΔXI shown in FIG. 5 corresponds to the distance between the vertices of the peaks PI and P2b, the distance ΔXO corresponds to the distance between the vertices of the peaks PI and P2a, and the positional deviation ΔX corresponds to the distance between the vertices of the peaks PI and P2a. It corresponds to the distance between each vertex of P2b. These are shown simultaneously in FIG.

For example, the light beam Ll forming the peak PI is sufficiently narrowed down by the action of the aperture 26, so that the peak PI can have a sufficiently sharp shape. This also applies to the beaks P2a and P2b.

In this embodiment, when determining the peak position, the area of the portion surrounded by each peak and the coordinate axis (hereinafter referred to as "beak area") is calculated. Then, the coordinate value that divides this peak area into two is determined as the peak position. According to such a peak position determination method, the one-dimensional image sensor 2
It is possible to determine the peak position in more detail than the spacing between elements in 9.

Another method for determining the peak position is to calculate the average position X using the light ffiI detected by each element of the one-dimensional image sensor 29 as a weight. It is also possible to use a method in which the average position XM is calculated based on the following [phase] formula and the average position XM is set as the peak position.

However, X indicates a coordinate position on the detection surface of the one-dimensional image sensor 29.

However, this method has the drawback that data that deviates from the average position XM is emphasized.

As mentioned above, in the method of setting the peak position at the coordinate position that bisects the peak area, the importance of all lights becomes equal,
Furthermore, since almost all of the received light is treated as valid data, there is an advantage that the accuracy of the peak position is increased.

As a technique for determining the peak position, for example, the technique disclosed in Japanese Unexamined Patent Publication No. 63-295935 can be used. This disclosed technology determines the center of gravity of a pentagon formed on a graph showing the correlation between the amount of light and the coordinate position as the peak position when light is received by, for example, five elements in a one-dimensional image sensor. The height of a triangle with a predetermined base having an area equal to the area of a pentagon is determined as the peak height, even if the peak position of the intensity of light incident on the image sensor is in a non-photoelectric conversion area between elements. This technology allows the peak position and peak height to be detected accurately. By applying this technique, it is also possible to determine peak positions in more detail than the spacing between elements.

FIG. 7 shows the peak position coordinates xl (see FIG. 6) of the beak P1 corresponding to the luminous flux Ll and the peak position coordinates x2a of the peak P2a (sixth (See figure) is a diagram showing each time change. The imaging positions of the light beams Ll and L2 vary over time as shown by curves 11 and 12, respectively, due to the influence of mechanical vibrations and air fluctuations. however,
This variation in the imaging position causes the light beam L1. appears equally with respect to L2 and therefore this luminous flux Ll. The distance ΔXO between each imaging position of L2 shows almost no change over time as shown by the curve IO, and in experiments by the inventors of the present invention, the distance ΔXO is ±2/1 0 0
Only the time change of 0 (gu++) was measured.

In this way, the distance ΔXO can be accurately measured by eliminating the influence of mechanical vibrations.

The same holds true when the sample solution is placed in the first chamber 71 of the cell 27, so that the distance ΔXI shown in FIG. 5 can be measured accurately. As a result, the positional deviation ΔX can be determined with high accuracy. That is, in this embodiment, since the light beam L2 that has passed through the sample solution and the light beam L1 that has passed only through the solvent are simultaneously detected, the influence of mechanical vibrations, air fluctuations, etc. can affect the light beam LI. This appears in common as a change in each imaging position of L2, and therefore, the distance between the two can be measured accurately by canceling out the above-mentioned error factors.

For example, if the distance l between the cell 27 and the one-dimensional image sensor 29 is 300 (mm) and the angle θ is 45 degrees, the minimum detection sensitivity Δnmlm is 2X300X1 = 1.9X10-' . As mentioned above, since the influence of mechanical vibrations and the like is extremely suppressed, the detection sensitivity shown by the above equation (2) can be easily obtained.

As described above, in the configuration of this embodiment, mechanical components such as the correction glass plate 7 in the first prior art shown in FIG. Since the system does not include any driven components and each component remains stationary throughout the measurement operation, there is no undesirable vibration, and the reduced number of parts also contributes to lower costs. It will be profitable. Moreover, as described above, the measurement of the positional deviation ΔX of the imaging position of the light beam L2 is performed with high precision, regardless of mechanical vibrations or changes over time of the optical base (not shown), and therefore the refraction Measurements of rates can now be made with extremely high precision.

Furthermore, from the light from the single light source 2l, two luminous fluxes Ll.
The light beams L1 and L2 are further narrowed down by the aperture 26 to ensure that they are divided and are incident on the cell 27, respectively.The light beam L2 transmits both the sample solution and its solvent, and the light beam L1 transmits only the solvent. A slit 24 that transmits light from the light source and forms light beams Ll and L2 from the light source is arranged so as to have an optically conjugate positional relationship with the one-dimensional image sensor 29 with respect to the imaging lens 25. The images of the apertures 24a and 24b are clearly formed on the detection surface of the one-dimensional image sensor 29. Thereby, the distance ΔX1 between the imaging positions of the respective images of the apertures 24a and 24b of the slit 24 by the one-dimensional image sensor 29 can be measured with high precision.

In addition, as a cell for separately accommodating the sample and the reference, instead of the cell 27 as shown in FIG. 4, a cell container constituted by a rectangular prism-shaped transparent casing as shown in FIGS. 8 to 11, respectively, may be used. The internal space of 40 is partitioned by a transparent partition plate 4l having a V-shaped cross section, so that, for example, a sample whose refractive index is to be measured is placed in one chamber 42, and a reference whose refractive index is known is placed in the other chamber 43. A cell may also be used. In this case, if the light beam L2 is made to pass through the partition plate 4l, this light beam L2 will pass through the cell once and will be deflected twice due to the difference in refractive index between the sample and the reference.
The amount of deflection is doubled, and therefore the accuracy of refractive index measurement can be further improved.

Another example of the cell is the configuration shown in FIG. 12. In this cell, a V block 45 is made of a transparent solid material with a known refractive index and has a V-shaped recess 45a, and a sample 46 of solid or liquid whose refractive index is to be measured is placed in the recess 45a. It is intended to be placed or accommodated. In this case, block 45 functions as a reference.

In addition to the above-mentioned cell, there is also an arbitrary cell in which when two light beams are incident simultaneously, one light beam passes through the sample and the reference, and the other light beam passes only through either the sample or the reference. Cells may also be used. Alternatively, the configuration may be such that both light beams pass through the sample and the reference, but in this case, the angles between the two light beams and the partition plate that partitions the sample and the reference are made different from each other. It is necessary to ensure that the traveling directions of the respective light beams after deflection are not parallel to each other. Furthermore, the sample and reference need not be fluids such as liquids, but may be solids.

FIG. 13 is a plan view showing a simplified basic configuration of another embodiment of the present invention, and FIG. 14 is a front view thereof.

In FIGS. 13 and 14, parts corresponding to those shown in FIGS. 1 and 2 described above are designated by the same reference numerals.

In this embodiment, in place of the cell 27 used in the embodiment shown in FIGS. 1 and 2, a cell 50 having a structure similar to the price cell shown in FIG. 22 is used, for example. Then, the luminous flux L2 passes through this cell 50, and the luminous flux L2
l propagates in the air outside the cell 50. The cell 50 has a luminous flux L
The internal space is divided into two chambers by a partition plate arranged diagonally with respect to 2, and one chamber houses the sample whose refractive index is to be measured, and the other chamber houses the reference whose refractive index is known. It has been accommodated. This reference may be air.

According to such a configuration, the light beam L2 is deflected in accordance with the refractive index difference between the sample and the reference, and the light beam Ll is not deflected due to the refractive index difference, so that the one-dimensional image sensor 29 The detected luminous flux Ll,
The distance between each imaging position of L2 corresponds to the refractive index difference. The same operations and effects as in the embodiments shown in FIGS. 1 and 2 can be achieved.

Note that as shown in FIG. 15, the light flux Ll passing outside the cell 50
An empty cell 53 having the same configuration as the cell 50 and containing air in both chambers may be interposed in the optical path of the image sensor 29, in which case the light beam L1. By detecting the distance between each imaging position of L2, the influence of the cell 50 on the luminous flux L2 can be canceled out, so that the measurement accuracy of the refractive index can be further improved. Further, instead of the empty cell 53, a faithful cell made of a transparent solid material may be used.

Further, as the cell 50, for example, a cell similar to the cells shown in FIGS. 8 to 11 having a partition plate having a V-shaped cross section,
It is also possible to use a cell such as the one shown in FIG. 12, in which case the luminous flux L2 passes through the cell and
Since the beam is deflected twice, the measurement accuracy of the refractive index is further improved.

Note that in each of the embodiments described above, the slit 24
Two separate luminous fluxes LI. Although the slit 24 is described above, a light transmitting member carrying an image having at least two identification points may be used instead of the slit 24. That is, the light transmitting member is, for example, as shown in FIG.
1, 32 (shown with diagonal lines in FIG. 16) may be formed into a pattern, and the light-shielding portions 31 and 32 may be used as identification points, or as shown in FIG. 16
The light transmitting member shown in the figure may be one in which the light shielding part and the light transmitting part are reversed.

Further, the shape of the light shielding portion is arbitrary, and may be circular as shown in FIG. 18, for example. Furthermore, as shown in FIG. 19, a rectangular light shielding section 36 is formed on the transparent plate-like member 35, for example, at both ends 36a of the light shielding section 36. 36b
may be made into two identification points. Also,
As shown in FIG. 20, a scale 38 may be formed on the surface of a transparent plate-like member 37. By using a light transmitting member carrying an image including at least two identification points in this manner, it is possible to obtain the amount of deflection of the light transmitted through the sample and the reference based on the detection output of the image sensor 29.

Furthermore, in each of the embodiments described above, an aperture 26 having a pinhole formed on the optical axis of the imaging lens 25 is used as the aperture member, and the aperture 26 is arranged close to the back of the imaging lens 25. However, the shape and arrangement of the aperture member are such that the incident light on the one-dimensional image sensor 29 is
What is necessary is to ensure that the light that has passed through the partition plate 27b of the cell 27 and the light that has not passed through the cell 27 are separated. That is, in the configuration of FIGS. 1 and 2, FIGS. 13 and 14, or FIG. 15, instead of the aperture 26,
A diaphragm member having one or two via holes formed therein may be placed at an arbitrary position between the slit 24 and the one-dimensional image sensor 29.

That is, as shown in FIGS. 1, 13, and 15, for example, a diaphragm member 26a composed of a plate-shaped body having two via holes is used to form an image with a condensing lens 23 instead of an aperture 26. It may also be placed between the lens 25 and the like. The number of such aperture members does not need to be one, and a plurality of aperture members may be provided on the optical path from the slit 24 to the one-dimensional image sensor 29.

Further, the light-shielding cut plate 30 is provided between the aperture 26 and the cell 27, for example. It may be arranged between the cell 27 and the reflecting mirror 28, or a plurality of light shielding cut plates may be used.

Furthermore, in each of the above-mentioned embodiments, the optical path is folded back using the reflecting mirror 28 to make the overall configuration compact, and the light beams Ll and L2 are each transmitted through the cell 27 twice, so that the light beams are deflected. Although the measurement accuracy is improved by increasing the amount of deflection of the light beam L2,
A one-dimensional image sensor 29 is arranged behind the cell 27 without using a reflecting mirror 28 to form a linear configuration, and the luminous fluxes Ll, L
2 may each pass through the cell 27 only once.

Various other design changes can be made without changing the gist of the present invention.

Effects of the Invention As described above, the differential refractometer of the present invention does not include any mechanically driven components, so mechanical vibrations can be eliminated and refractive index can be measured with high precision. In addition, the number of parts can be reduced, contributing to cost reduction. In addition, since the light that has passed through the two identification points of the image carried by the light-transmitting member is detected simultaneously by the image sensor, even if the image formation position of the light that has passed through one of the identification points is due to vibrations, air fluctuations, etc. Even if the position shifts, the imaging position of the light that has passed through the other identification point will show a similar change. Therefore, by determining the distance between the imaging positions of both lights, it is possible to determine the imaging position caused by the vibrations, air fluctuations, etc. Positional deviations can be offset.

Furthermore, since the light transmitting member and the image sensor are arranged in a conjugate positional relationship with respect to the lens,
The image of the light-transmitting member can be clearly formed on the detection surface of the image sensor, and the diaphragm member reliably separates the light that has passed through the two identification points on the light-transmitting member. Therefore, both lights can be reliably separated on the detection surface of the image sensor. As a result, the distance between the imaging positions of the light that has passed through the two identification points of the light-transmitting member and passed through the sample and reference inside the cell, and the light that has passed only one of the sample and reference or outside the cell. The measurement accuracy is good. This can also contribute to improving the accuracy of refractive index measurement.

[Brief explanation of drawings]

1 is a plan view showing a simplified basic configuration of a differential refractometer according to an embodiment of the present invention; FIG. 2 is a front view thereof; FIG. 3 is a front view of the slit 24; 5 is a perspective view showing the principle of refractive index measurement, FIG. 6 is a diagram showing the output intensity of the one-dimensional image sensor 29, and FIG. 7 is a diagram showing each of the beaks PI and P2a in FIG. 6. FIG. 8 to FIG. 12 are cross-sectional views illustrating applicable cells, and FIG. 13 is a plan view showing a simplified basic configuration of another embodiment of the present invention. 14 is a front view thereof, FIG. 15 is a plan view showing the basic configuration of still another embodiment of the present invention, and FIGS. 16 to 20 illustrate applicable light transmitting members, respectively. 21 is a simplified plan view showing the configuration of the first prior art, FIG. 22 is a sectional view of the cell 5, and FIG. 23 is a plan view illustrating the function of the correction glass plate 7. , FIG. 24 is a front view showing a simplified configuration of the second prior art. 2l... light source, 24... slit (light transmitting member),
25... Imaging lens, 26... Aperture (diaphragm member) 27... Cell, 29... One-dimensional image sensor, 53... Empty cell 21... Light source 24... Slit 25. ... One-dimensional lens 26...Averture 27...Cell 29...One-dimensional image sensor (Figure 1) Figure 29 Figure 4 Figure 7 Figure 8 Figure 9 Figure 1o Figure 11 Figure 12 Light source slit imaging lens aperture one-dimensional image sensor cell Figure 13 Light source slit imaging lens aperture one-dimensional image sensor cell Empty cell Figure 20 38 Figure 21 Figure p1 6-9 Figure 24

Claims (1)

[Scope of Claims] 1. A light source, a light transmitting member carrying an image having at least two identification points, a lens for condensing the light source light transmitted through the light transmitting member, and a light transmitting member with respect to the lens. an image sensor placed at a position conjugate to the member; a sample whose refractive index is to be measured and which is placed at any position between the light-transmitting member and the image sensor; and a reference having a reference refractive index. and a cell that is arranged in any position between the light transmitting member and the image sensor to respectively narrow down the light that has passed through the two identification points of the light transmitting member. A differential refractometer comprising: an aperture member that allows at least one of the lights to pass through the cell. 2. A claim characterized in that the light that has passed through either one of the two identification points passes through both the sample and the reference in the cell, and the light that has passed through the other identification point passes outside the cell. Item 1. Differential refractometer according to item 1. 3. The differential refractometer according to claim 2, wherein the light passing outside the cell propagates in the air. 4. The differential refractometer according to claim 2, wherein an empty cell containing air is interposed in the optical path of the light passing outside the cell. 5. Claim 2, characterized in that a solid cell made of a transparent solid material is interposed in the optical path of the light passing outside the cell.
Differential refractometer as described. 6. The aperture member converts the light that has passed through the two identification points onto the cell into a refractive index difference between the light that passes through one of the sample and the reference and the light that passes through both the sample and the reference. 2. The differential refractometer according to claim 1, wherein the differential refractometer focuses on light that is deflected accordingly.